The proper design of an AC substation earthing grid involves ensuring that the substation environment and immediate perimeter is free from the possibility of fatal electric shock and that it provides a low impedance path for fault and earth leakage currents. Engineers are faced with a variety of national standards incorporating apparently differing formulae for the calculation of safe touch and step potentials.

ERA Technology Ltd is the UK agent for Ground ROD 2006, a Microsoft Excel spreadsheet which can perform calculations for the design of AC substation earthing systems.

Calculations

By simple selection, Ground ROD 2006 can perform earthing calculations in accordance with the following standards:

	IEEE standard 80 (both 2000 and 1986 editions)
	BS 7354 - 1990
	EA Technical Specification 41-24

In addition, Ground ROD 2006 incorporates a set of newly developed equations providing calculation results which are consistent with test results as published in the EPRI EL-3099 document. In this respect, the Ground ROD 2006 calculations give more accurate results than any other program available. Ground ROD 2006 includes calculations for:

	grid resistance
	grid current
	grid voltage rise
	mesh voltage
	touch voltage
	step voltage
	HOT distance

allowable touch and step voltages (with and without a surface layer of stones).

Other features

Ground ROD 2006 comes in a very easy-to-use format and can generate detailed calculation reports for insertion into other reports. The spreadsheet also provides a host of peripheral information such as formulae and guidance on AC substation earthing design.

Other features provided in Ground ROD 2006 are:
	Wenner and Tagg Slope test reports.
	inclusion of overhead line earthing, cables and local earthing.
	calculation of the surface voltage profile over and beyond the grid corners.
	inclusion of up to 4 grids at a site taking into account their relative spacing.
	facility to check voltage differences for a grid containing different mesh sizes

Calculations

To view calculations in action click here >>>

benefits

The Ground ROD 2006 software provides clients with:
	an effective means to ensure correct and safe substation earthing design and practice
	full functionality and versatility surrounding compliance with current standards
	the ability to perform calculations consistent with EPRI EL-3099 test results
	a familiar and easy-to-use software interface
	a value-for-money solution.

why ERA?

As well as supplying the Ground ROD 2006 software and by drawing on its expertise in power systems, ERA provides design and consultation services on AC substation earthing systems.  Ground ROD 2006 also compliments the ERACS suite of power systems analysis software available from ERA Technology.